People's perceptual reports are biased toward percepts they are motivated to see. The arousal system coordinates the body's response to motivationally significant events and is well positioned to regulate motivational effects on perceptual judgments. However, it remains unclear whether arousal would enhance or reduce motivational biases. Here, we measured pupil dilation as a measure of arousal while participants (N = 38) performed a visual categorization task. We used monetary bonuses to motivate participants to perceive one category over another. Even though the reward-maximizing strategy was to perform the task accurately, participants were more likely to report seeing the desirable category. Furthermore, higher arousal levels were associated with making motivationally biased responses. Analyses using computational models suggested that arousal enhanced motivational effects by biasing evidence accumulation in favor of desirable percepts. These results suggest that heightened arousal biases people toward what they want to see and away from an objective representation of the environment.

We often make decisions on behalf of others, such as pickingout gifts or making restaurant recommendations. Yet, withoutdirect access to others’ preferences, our choices on behalf ofothers depend on what we think they like. Across twoexperiments, we examined whether and how accuratelypeople are able to infer others’ preferences by observing theirchoices. Our results suggest that people are capable of makingreasonably accurate predictions about what others will choosenext, given what they have chosen before. These results laythe groundwork to systematically study how people makenovel predictions about others’ preferences, and whendifferent strategies might be appropriate.